In a line

Delegates at next month's Linear Motion Masterclass will learn about emerging technologies and key techniques from experts in the field. Lou Reade reports

An expert in precision linear motion and one of Europe's leading engineering research companies head the list of participants at the forthcoming Linear Motion Masterclass - the latest in Eureka's series of Design Days.
Professor Paul Shore, director of Cranfield University's Precision Engineering Centre, is one of two independent speakers at the event. Prof Shore will explain how high precision linear motion is a critical factor in the BoX (Big OptiX) machine, an ultra-precision free form grinding and measuring machine that is used to produce optical parts for telescopes.
At the same time, there will be a presentation from Philips Applied Technologies, which has developed a number of linear motion technologies - ranging from a magnetic levitation device to a linear motor that moves in two axes simultaneously. The latter research was led by Philips senior scientist Dr Georgo Angelis.
"To control the second axis, we just add a second commutation algorithm to the software controller, which sends appropriate signals to the linear motor amplifier, and appropriate current to the coils," he told Eureka in a recent interview.
The technology, dubbed Nforcer, is a modification to traditional linear motor design: a set of coils, which traditionally sits between two rows of magnets, has been shifted so that their lower horizontal section sits in the magnetic field. This means that force and motion can be generated in the vertical direction as well as in the horizontal direction.
"Around half the linear motors on the market today could adopt this technology very easily," says Angelis. "There are so many benefits from this technology that we are expecting a lot of interest."
Shore's BoX machine is a precision grinding machine that uses highly symmetrical structures and low mass, high power density and high temperature controlled sub-systems along with nanometre precision positioning control.
Dynamic stiffness is at the heart of the machine's design, as any vibration when grinding ceramic mirror segments would damage the surface. Cranfield claims that it can grind around 10 times faster than conventional machines.
A spindle head carriage is driven by two linear motors along hydrostatic guideways. The 17 tonne machine can grind objects up to 2m in diameter. Cranfield recently received an enquiry from China to buy a machine.
"Traditionally, the UK has always had a number of facilities capable of undertaking large optics projects," says Shore. "With continued investment, we can once again become a recognised world leader in this important technology field."
The format of the Design Day is unchanged: the morning is devoted to technical presentations, while the afternoon turns into a series of hands on workshops led by the event sponsors.
The sponsors of the event are Aerotech (linear motors), Igus (bearings), Renishaw (encoders) and Steinmeyer (ballscrews).?Each will help delegates to understand key aspects of linear motion technology through short technical presentations, hands-on training workshops and consultancy sessions. More details on the workshops are included in the box panel.
The event takes place at the Kaetsu Centre in Cambridge on Tuesday 18 March 2008. To book places at the event, visit the Design Days website ( or call Kerry Wilkins ( on 01322 221144.

Linear workshops
Workshops are key to the Design Days, and this year's subjects are already confirmed. The four event sponsors - Aerotech (linear motors), Igus (bearings), Renishaw (encoders) and Steinmeyer (ballscrews) - will guide delegates through key aspects of the subject.
Renishaw will present an overview of encoder feedback systems and their influence on the accuracy of movement and control, with practical examples of their integration. The workshop also includes detailed explanation of how laser calibration can support the design process. The sessions are led by Renishaw's James McMath and Gary Swan.
Steinmeyer explains what can be done with a ballscrew to enable the servo drive to follow the desired path. Its workshop will also challenge delegates to select a particular ballscrew for a particular application.
Aerotech guides delegates through the steps of specifying a linear motor - which are well known for their accuracy and speed. It will lay out the key considerations for considering a linear motor based system.
And finally, Igus guides delegates through the fundamentals of linear bearings: it's no good thinking about bearings after you've designed your precision linear system, says the company - they are fundamental to the design, so need to be considered right at the start of the process.

Tom Shelley

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